Big Questions in Science
Big Questions in Science, fall 2012. SdH, AUC   2
   Color and spectra   Atoms   Schrödinger’s cat   Radioactivity              Big Questions in Science, fall 2012. SdH...
 Light is a wave made ofdifferent wavelengths Blue light has shortwavelength. Scattered all around atmosphere.          ...
Big Questions in Science, fall 2012. SdH, AUC   5
   Cathode ray tube    1. Three electron guns    2. Electron beams    3. Focusing coils    4. Deflection coils    5. Anod...
•   (Semi-) vacuum tube•   Metal electrodes, high voltage in between•   Postitively charged atoms attracted to cathode (ne...
   Faraday: electrical current bent by a magnet.   Thomson: electrical current consists of    particles much smaller tha...
Big Questions in Science, fall 2012. SdH, AUC   9
   Ernest Rutherford: radiation consists of:     Beta-rays. Could be bent, electrons.     Alpha-rays. Could be bent, mu...
   Rutherford: researched thorium, found    emanation and radioactivity. Bombarded    platinum foil with alpha particles,...
   Rutherford: second, “planetary” model    (inspired by Lord Kelvin).             Big Questions in Science, fall 2012. S...
Big Questions in Science, fall 2012. SdH, AUC   14
Different elements have different ‘absorption spectra’, specific wavelengths that theyabsorb (or emit).                   ...
Planck’s lawBig Questions in Science, fall 2012. SdH, AUC   16
   Assumption Planck needed to make: light    carries energy in discrete amounts.   Each ‘energy packet’ has energy h   ...
   Fascinated by planetary model.   Putting things together: quantum hypothesis    applied to atom.   Atomic numbers ex...
Big Questions in Science, fall 2012. SdH, AUC   19
   Radiatioactive decay is random.   Same true for photon emission by atom:    unpredictable.             Big Questions ...
PET scan   X-rays                    21
   As long as radiation is not measured, the    atom is in two states (decay/non-decay). This    is called a superpositio...
   The single-slit experiment              Big Questions in Science, fall 2012. SdH, AUC   23
http://www.universetoday.com/83380/double-slit-experiment/Big Questions in Science, fall 2012. SdH, AUC                   ...
http://www.hitachi.com/rd/research/em/doubleslit.html                           Big Questions in Science, fall 2012. SdH, ...
Waves that go through the slits interfere with each                                                                       ...
http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/Big Questions in Science, fall 2012. SdH, AUC             ...
   Electrons and photons behave as waves while    in transit: interference.   Detected as particles on the screen.   In...
   de Broglie: if photons are both waves and    particles, particles behave as waves.     Planck relation:              ...
   Waves of high frequency (short wavelength)    are sharply localized, waves of low frequency    (long wavelength) are s...
Electron microscope            Quantum computing                                  http://www.science.uva.nl/onderwijs/thes...
Big Questions in Science, fall 2012. SdH, AUC   32
Big Questions in Science, fall 2012. SdH, AUC   33
Big Questions in Science, fall 2012. SdH, AUC   34
   Compare Bohr’s model of the atom with the    Solar System.     1) Similarities. 2) Where analogy breaks down.   What...
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6 From Atoms To Color TV

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Big Questions in Science series, (6 of 9). Class taught at AUC (University of Amsterdam) during the 2012-2013 fall semester.

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6 From Atoms To Color TV

  1. 1. Big Questions in Science
  2. 2. Big Questions in Science, fall 2012. SdH, AUC 2
  3. 3.  Color and spectra Atoms Schrödinger’s cat Radioactivity Big Questions in Science, fall 2012. SdH, AUC 3
  4. 4.  Light is a wave made ofdifferent wavelengths Blue light has shortwavelength. Scattered all around atmosphere. Ni (78%) O (21 %) Big Questions in Science, fall 2012. SdH, AUC 4
  5. 5. Big Questions in Science, fall 2012. SdH, AUC 5
  6. 6.  Cathode ray tube 1. Three electron guns 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Separating beams 7. Phosphor layer 8. Close-up of screen http://en.wikipedia.org/wiki/File:CRT_color_enhanced.png Big Questions in Science, fall 2012. SdH, AUC 6
  7. 7. • (Semi-) vacuum tube• Metal electrodes, high voltage in between• Postitively charged atoms attracted to cathode (neg.)• Kicked off electrons attracted to anode (positive charge) Big Questions in Science, fall 2012. SdH, AUC 7
  8. 8.  Faraday: electrical current bent by a magnet. Thomson: electrical current consists of particles much smaller than atoms. Mass 1600 smaller than hydrogen. Röntgen: new type of ‘cathode’ radiation. Becquerel: uranium emits Röntgen radiation. Marie Curie researched other substances. Big Questions in Science, fall 2012. SdH, AUC 8
  9. 9. Big Questions in Science, fall 2012. SdH, AUC 9
  10. 10.  Ernest Rutherford: radiation consists of:  Beta-rays. Could be bent, electrons.  Alpha-rays. Could be bent, much heavier, positive charge. Helium ions.  Gamma-rays. Röntgen radiation. UV Suggested internal structure of atoms. Big Questions in Science, fall 2012. SdH, AUC 10
  11. 11.  Rutherford: researched thorium, found emanation and radioactivity. Bombarded platinum foil with alpha particles, reflected in all directions. Conclusion: mass concentrated in the nucleus. Big Questions in Science, fall 2012. SdH, AUC 12
  12. 12.  Rutherford: second, “planetary” model (inspired by Lord Kelvin). Big Questions in Science, fall 2012. SdH, AUC 13
  13. 13. Big Questions in Science, fall 2012. SdH, AUC 14
  14. 14. Different elements have different ‘absorption spectra’, specific wavelengths that theyabsorb (or emit). Big Questions in Science, fall 2012. SdH, AUC 15
  15. 15. Planck’s lawBig Questions in Science, fall 2012. SdH, AUC 16
  16. 16.  Assumption Planck needed to make: light carries energy in discrete amounts. Each ‘energy packet’ has energy h Big Questions in Science, fall 2012. SdH, AUC 17
  17. 17.  Fascinated by planetary model. Putting things together: quantum hypothesis applied to atom. Atomic numbers explain properties of atoms. Sommerfeld refined version. Big Questions in Science, fall 2012. SdH, AUC 18
  18. 18. Big Questions in Science, fall 2012. SdH, AUC 19
  19. 19.  Radiatioactive decay is random. Same true for photon emission by atom: unpredictable. Big Questions in Science, fall 2012. SdH, AUC 20
  20. 20. PET scan X-rays 21
  21. 21.  As long as radiation is not measured, the atom is in two states (decay/non-decay). This is called a superposition. Property is only determined once a measurement is made. Big Questions in Science, fall 2012. SdH, AUC 22
  22. 22.  The single-slit experiment Big Questions in Science, fall 2012. SdH, AUC 23
  23. 23. http://www.universetoday.com/83380/double-slit-experiment/Big Questions in Science, fall 2012. SdH, AUC 24
  24. 24. http://www.hitachi.com/rd/research/em/doubleslit.html Big Questions in Science, fall 2012. SdH, AUC 25
  25. 25. Waves that go through the slits interfere with each other. Big Questions in Science, fall 2012. SdH, AUC 26http://russherman.com/Talks/FirstThreeMinutes_CollegeDay.pdf
  26. 26. http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/Big Questions in Science, fall 2012. SdH, AUC 27
  27. 27.  Electrons and photons behave as waves while in transit: interference. Detected as particles on the screen. Interference pattern disappears if observation. No way to predict where single photon ends up: intrinsic unpredictability. Only probabilities. Big Questions in Science, fall 2012. SdH, AUC 28
  28. 28.  de Broglie: if photons are both waves and particles, particles behave as waves.  Planck relation: . Matter: .  Frequency proportional to speed (squared). Big Questions in Science, fall 2012. SdH, AUC 29
  29. 29.  Waves of high frequency (short wavelength) are sharply localized, waves of low frequency (long wavelength) are spread out. Small Large Large Small Big Questions in Science, fall 2012. SdH, AUC 30
  30. 30. Electron microscope Quantum computing http://www.science.uva.nl/onderwijs/thesis/apart/phys/thesis.php?start=181&level=bachelor Resolution ~ wavelength 0.1 to 0.5 nm 31
  31. 31. Big Questions in Science, fall 2012. SdH, AUC 32
  32. 32. Big Questions in Science, fall 2012. SdH, AUC 33
  33. 33. Big Questions in Science, fall 2012. SdH, AUC 34
  34. 34.  Compare Bohr’s model of the atom with the Solar System.  1) Similarities. 2) Where analogy breaks down. What is the role of the hydrogen atom in the development of modern quantum mechanics?  Hint: consider Kuhn’s notion of ‘exemplar’.  Think of similar examples in Newtonian physics and in the theory of relativity. Big Questions in Science, fall 2012. SdH, AUC 35

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